In many applications, such as gas turbine engines, rotating components, such compressor and turbine disks, are subjected to high speed rotational (spin) testing to detect imbalances and structural abnormalities at different design and testing stages. Current techniques in the state of the art do not provide high level, continuous vibratory spin excitation, the excitation typically is extremely transient. In other words, these techniques do not provide a realistic simulation of actual engine vibration conditions. A variety of sources produce different engine vibrations during actual engine operation.
The capability to excite rotating components (hardware) dynamically during experimental/design testing provides a significant advantage by demonstrating possible high level component responses that may cause expensive engine damage and time out of service. Prior art approaches have used electromagnets and air jets to impart vibrations to the spinning disk. But, electromagnets overheat, besides not being very powerful ( taking into account realistic costs for the electromagnets and associated power supplies). Continuous use of adequate electromagnets during extensive spin testing can require exotic magnet cooling schemes. Generally, air jets are useful only for mono-frequency testing, and the test data is transient (temporary) because the air jet decelerates the rotating disk.
Piezoelectric devices are capable of imparting mechanical energy (vibrations) to objects in response to an electrical signal. These devices have broad bandwidth characteristics and have been used for stationary fatigue testing, U.S. Pat. No. 3,563,086 being an example.